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Why do swim clocks stop at hundredths?

5th GradeDecimalsabout 3 minCCSS 5.NBT.A.1CCSS 5.NBT.A.3.bCCSS 5.NBT.A.4

Split a second into tenths, hundredths and thousandths at the wall of an Olympic pool.

Lesson Plan

Explore decimal place value to the thousandths, then compare and round decimals.

  1. Question: Ask what students spot and what they are curious about. Read “How far does he swim in a hundredth?” aloud. Have each student guess and say why.

  2. Question: Read “Won by a thousandth. Was she faster?” aloud. Have partners explain their guesses to each other.

  3. Big idea: Pause. Ask a student to say the idea in their own words.

  4. Real-world application: Ask: Where else have you seen this?

  5. Your turn: Have students try their own. Ask them to predict before they test.

How to run it

  1. Whole classPut the lesson on the board. At each choice the class votes, then you select the winner.
  2. SoloShare the link, QR code, or post to Google Classroom. Each student gets to take their own path.